1. Field of the Invention
The present invention relates to an optical element which realizes various optical effects by forming a photoinduced refractive-index changing region at a predetermined position of a light guide, a method thereof, and an optical device mounted with the same optical element. For the optical element, various optical elements such as an optical fiber, an optical integrated circuit, and a simple lens can be mentioned.
2. Description of the Prior Art
An optical element for realizing various optical effects is formed by forming, in a core or light guide of an optical fiber to propagate light signals, functional components such as a lens, a mirror, a diffraction grating, and a polarizer to control physical properties of light. An optical element is fabricated by mounting this optical element on an optical substrate or the like. On the other hand, phenomena have been confirmed such that, by irradiating a focused pulse laser light with a femtosecond-order (10−12 to 10−15 seconds) pulse width onto the inside of a transparent material such as glass, conditions of an atomic arrangement, a valence, an atomic defect and the like in the vicinity of a light focusing portion are changed, and refractive index is made higher than that of a portion which has not irradiated with the pulse laser light or a region where refractive index is periodically modulated is formed in the vicinity of a light focusing portion as a result of interference of the pulse laser light with plasma generated in the vicinity of the light focusing portion, and these have been called a photoinduced change in refractive index, a nano-grating formation or the like.
In the present specification, the above-described grating formation is also considered as a mode of change in refractive index, and these phenomena such as a change in refractive index and a nano-grating formation will be generally referred to as “photoinduced refractive-index change.”
The foregoing optical element is generally formed by coupling separately prepared functional components such as a lens, a mirror, and a diffraction grating to an optical substrate, however, since the functional components are complicated in structure and also large in size, there is a problem such that the optical element itself is increased in size.
Furthermore, for manufacturing the optical element, a step for manufacturing an optical substrate, a step for manufacturing functional components such as a lens, a mirror, and a diffraction grating, and a step for mounting these functional components on the optical substrate are necessary, therefore, manufacturing processes are complicated, and the manufacturing cost is also increased.
In addition, even when coupling of the functional components to an optical fiber is intended, since the core diameter of the optical fiber is small, high-precision processing is difficult, and the manufacturing cost is increased.
Therefore, it is an object of the present invention to provide a small-sized and easily-manufacturable optical element on which functional components such as a lens, a mirror, and a diffraction grating can be integrally formed and which can realize a variety of optical effects.
Moreover, it is an object of the present invention to provide a method for manufacturing an optical element whereby a small-sized optical element can be simply and swiftly manufactured by integrally forming functional components such as a lens, a mirror, and a diffraction grating after an optical substrate manufacturing step.
Furthermore, it is an object of the present invention to provide an optical device mounted with the above-described optical element.